ISOKINETIC ECCENTRIC EXERCISE AS A MODEL TO INDUCE AND REPRODUCE PATHOPHYSIOLOGICAL ALTERATIONS RELATED TO DELAYED-ONSET MUSCLE SORENESS

Physiological alterations following unaccustomed eccentric exercise in an isokinetic dynamometer of the right m. quadriceps until exhaustion were studied, in order to create a model in which the physiological r esponses to physiotherapy could be measured. In experiment I (exp. I), seven selected parameters were measured bilaterally in 7 healthy subj ects at day 0 as a control value. Then after a standardized bout of ec centric exercise the same parameters were measured daily for the follo wing 7 d (test values). The measured parameters were: the ratio of pho sphocreatine to inorganic phosphate (PCr/P-i), the ratio of inorganic phosphate to adenosintriphosphate (Pi/ATP), the ratio of phosphocreati ne to adenosintriphosphate (PCr/ATP) (all three ratios measured with P -31-nuclear magnetic resonance spectroscopy), dynamic muscle strength, plasma creatine kinase (CK), degree of pain and ''muscle'' blood flow rate ((133)Xenon washout technique). This was repeated in experiment II (exp. II) 6-12 months later in order to study reproducibility. In e xperiment III (exp. III), the normal fluctuations over 8 d of the seve n parameters were measured, without intervention with eccentric exerci se in 6 other subjects. All subjects experienced pain, reaching a maxi mum 48 h after eccentric exercise in both exp. I and II. A systematic effect over time for CK (increasing 278% resp. 308%), muscle strength (decreasing more than 10%), PCr/Pi (decreasing 31% resp. 43%) and Pi/A TP (increasing 55% resp. 99%) was found in both exp. I and II(P<0.05), but not in exp. III. No significant difference was observed between e xp. I and II for CK, blood-flow rate, concentric muscle strength, PCr/ Pi, Pi/ATP and PCr/ATP, It is concluded that pathophysiological altera tions in m. quadriceps following eccentric exercise can be induced and can be reproduced after an interval of 6 months. Thus, this model can be used to study the effects of physiotherapy.